Temperature responsive device



D. T. LANG TEMPERATURE RESPONSIVE DEVICE Sept. 25, 1956 2 Sheets-Sheet 1Filed Oct. -12, 1954 DE LME R ,T. LANG,

- IN VEN TOR.

A TTORNE Y PRESSURE pt 1956 D. T. LANG 2,764,651

TEMPERATURE RESPONSIVE DEVICE Filed Oct. 12, 1954 2 Sheet's-Sheet 2 INPOUNDS PER SQUARE INCH DELMER T. LANG, INVENTOR.

ATTORNEY United States Patent TEMPERATURE RESPONSIVE DEVICE Delmer T.Lang, Palos Verdes Estates, Califl, assignor,

by mesne assignments, to Walter Kiddo-Pacific, a corporation ofCalifornia Application October 12, 1954, Serial No. 461,828 14 Claims.(Cl. 200-140) This invention relates to a temperature responsive devicehaving as the temperature responsive element thereof a liquid underpressure in which device the rate of change of pressure isextraordinarily high with respect to changes in temperature and to acombination therewith providing an unusually large movement of thepressure responsive device with such changes in pressure.

Many temperature responsive devices are known which are used in athermostat for controlling temperature of a system in accordance with agiven temperature. For many uses, however, it is desirable or necessaryto have in a thermostat a temperature responsive device which is highlysensitive to changes in temperature especially within a range oftemperatures near the control temperature.

1 have discovered, in accordance with my invention, that such adesirable temperature responsive device can be made which is highlysensitive to small changes of temperature within the range oftemperatures near the control temperature and that within thistemperature range the device is substantially snap-acting, with respectto the liquid in the internal volume in the sense of a very high rate ofchange of pressure with temperature.

Accordingly, it is an object of my invention to provide a temperatureresponsive device, especially useful in a thermostat, which is highlysensitive to changes in temperature within a range of temperatures nearthe operating or control temperature and which, near the controltemperature, is substantially snap-acting with respect to rate of changeof liquid pressure with temperature.

Other advantages and objects of my invention will be apparent to thoseskilled in the art to which my invention relates from the descriptionbelow.

Broadly, my invention comprises the combination of a liquid-lockedliquid confined within a temperature-sensitive element such as a bulb,connected to a means, such as a Bourdon tube, movably responsive tochanges in pressure within the internal volume of the system withsubstantially no change in internal volume. In this combination theinternal volume of the system is filled with liquid under the conditionof liquid lock, that is, liquid with no vapor or gas. That is, in thisdevice the entire internal volume of temperature sensing bulb andBourdon tube is filled with liquid-locked liquid with no vapor or gas sothat the change of pressure of the internal volume varies with thethermal expansion of the liquid in accordance with the averagetemperature of the liquid in the internal volume. Especially since thissystem, in accordance with my invention, has a high rate of increase ofpressure with increase of temperature, it preferably also has means forrelieving any excessively high pressure developed in the liquid of theinternal volume of the system to avoid damage to the temperatureresponsive system on overheating.

My invention will be illustrated and explained by the description belowof a specific embodiment thereof taken in conjunction with theaccompanying drawings in which:

Fig. 1 shows a device of my invention in cross-section.

Fig. 2 shows the device of Fig. 1- in elevation.

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Fig. 3 shows a modification of my invention.

Fig. 4 shows a plot of pressure with temperature of the liquid in theinternal volume of my device as shown in Fig. 3.

One specific embodiment of my invention will be described by particularreference to Fig. 1 in which is shown a temperature sensing bulb 1connected by tube 2 extending through hole 3 in circular base member 4.Covering the bottom and sides of base 4 a diaphragm 5 is afiixed to thebase member by silver brazing around the periphery thereof as shown at10. Into base member 4 Bourdon tube 6 is fixedly inserted by silverbrazing as shown at 7. End 8 of tube 2 extends into the hole 3 in base 4and communicates with hole 9 which in turn communicates with theinterior of the Bourdon tube 6. Both tube 8 and hole 9 are open at thebottom to the upper surface of diaphragm 5 so that the pressure of theliquid within the tube 8, hole 9, tube 2 and bulb 1 is applied to thediaphragm 5 as well as to the Bourdon tube. The diaphragm 5 fits assnugly as possible against the bottom contours of the base member 4, asshown in the drawing, and is silver brazed around the periphery of thisbase member as shown at 10 to make a sealed gastight connection betweenthe bottom of this base member 4 and the upper surface of the diaphragm5. The diaphragm is made of 0.005" flexible stainless steel sheet, andhas an annular rim conforming to annular rim 51 of the base member 4 andannular groove 52 conforming to the annular groove 53 of the basemember. Bulb 1, tubes 2 and 8, hole 9, and Bourdon tube 6 are completelyfilled with liquid under liquid lock condition so that the pressurewithin this internal volume varies in accordance with the thermalexpansion of the liquid in accordance with the average temperaturethereof.

On the outside of diaphragm 5 is a stainless steel pressure dome 11which by silver brazing at 12 around the outer periphery of base member4 is sealed to form a pressure container or chamber 13 about the outersurface of the diaphragm 5. This container is pressurized preferablywith gas at the pressure at which diaphragm 5 will expand under thepressure of liquid in tube 3 and hole 9 to relieve excessive pressure onthe internal volume of the temperature responsive system. Thus, gas maybe introduced into container 13 by way of pipe 14 which is then sealedoff as by soldering at 15.

The lower portion of the pressure dome may be enclosed in a housing 16if desired. Tubing 2 extends through hole 18 in presure dome 11. Thishole 18, however, is above the seal 12 between the pressure dome 11 andthe portion of the diaphragm 5 sealed at 10 to the periphery of the basemember 4.

The top surface of diaphragm 5 fits so snugly against bottom surface ofbase member 4 that there is substan tially no liquid therebetween andthe pressure in pressure r chamber 13 is not transmitted into the liquidin the internal volume of Bourdon tube 6, opening 9, tube 8, tube 2 andbulb 1. Thus the internal volume pressure is independent of the pressurein pressure container 13 until the internal volume pressure becomesgreat enough to cause the diaphragm 5 to move. This arrangement fordiaphragm 5 not only makes the internal volume pressure independent ofthe container or relief pressure up to an internal volume pressureapproximately equal to the relief pressure but also, because of therelative small volume of liquid within the Bourdon tube 6, opening 9 andtube 8 and the absence of any liquid between the diaphragm 5 and basemember 4, the whole device is relatively insensitive to any temperatureother than the temperature of the bulb 1. To further reduce volume ofliquid within the Bourdon tube the Bourdon tube is preferably filledwith metal plugging strips, as known in the art, to reduce the volume ofthe Bourdon tube to less than about of the unplugged Bourdon tubevolume.

The Bourdon tube 6, from its rigid support in base member 4, extendsupwardly into housing 19 which fits onto the upper portion of the basemember 4. The upper end of Bourdon tube it, carries electrical contact2ft ated to cooperate with electrical contact 22 to open close anelectrical circuit with movement of the Bourdon tube with variations inpressure of the liquid within the internal volume of the system as knownand understood in the art.

The arran n'ient shown in Fig. 1 may made by placing the uourdon tube 6within the slot or hole 7 by silver b zing. This fixes the Bourdon tubewith respect to the base member d. End of tube 2 is then insertedthrough hole 23 in upwardly extending wall 2i) of base member and end 3is bent and inserted in hole 3, which cstends all the way through basemember End B of tube 2.- is then silver brazed at 24 to hole 3 and thenthe end is cutoff flush with the bottom surface of base Silver brazingof "1" and 2.4 is preferably done at the same time. Hole 9 is thendrilled through the open portion of tube 5 through base member 4-through the Bourdon tube to communicate with the Bourdon tube. Thebottom surface of base 4 having openings for hole 9 and tube is thenmade smooth so that the diaphragm 5' can be made flush with the bottomsurface of base t. The diaphra m 5 is then placed to fit flush and insuch smooth contact with the bottom of base 4 as is possible and sealedby silver brazing at it around the periphery of base 4. Pressure dome 11is then placed in position and silver brazed as shown at 12 around theperiphery of base 4. The silver brazing at it and 12 is preferably doneat the same time.

In filling this unit with liquid in accordance with my inventionconnection may be made at tube which connects with bulb l. The internalvolume of bulb 1, tube 2 and Bourdon tube 6 is preferably outgassed asmuch as possible and placed under a vacuum. Liquid, preferably alsooutgassed as much as possible, is then run into the internal volumeunder pressure. The pressure of the liquid should be sufliciently abovethe vapor pressure so that at normal temperature conditions to which theliquid is subjected in operation no vapor appears and the entireinternal volume is filled with liquid in the liquid locked condition.Preferably to obtain the desired fill of liquid and adjust this devicefor operation at the same time, the pressure in chamber 13 against theoutside of the diaphragm is first provided by pumping gas into thisspace at the relief pressure which is safely above is the pressure ofoperation and below the pressure of rupture or bursting of any of theparts.

For example, the pressure in 13 may be 930 pounds per square inch. Ifthe thermostat is to be operated at 70 F. and the liquid is acetone, theinternal volume will, for example, be filled with acetone at a pressureof 400 pounds per square inch, a pressure sufficiently high to assureliquid lock at and near the temperature of operation, and the contactpoints 21 and 22 of thermostat adjusted for operation at this pressurewith the entire bulb l in a bath at the operating temperature of 70 F.It will be understood that the volume of the bulb is so much greaterthan the internal volume of tube 2 and Bourdon tube 6 that normaltemperature variations of this small volume of liquid will haverelatively little eflect on the system. Thus, this system will be set tooperate at 70 F. at an internal pressure of around 400 pounds per squareinch and with a relief pressure of 930 pounds per square inch which iswell above the operating pressure and yet safely below the rupture orbursting pressure of any of the elements of the device.

In operation the temperature sensing bulb 1 is subjected to thetemperature with respect to which control is to be effected. At thecontrol temperature the Bourdon tube, with increased pressure of theliquid in the internal the .nourdon tube.

n it is ssible to transform small changes in ternvith the arrangement inaccordance with my invention, .he rate of change of pressure withtemperature is so great mall amounts of overheating the pressure or rstsome element of the system. Howin crdance with this embodiment of myinvent n, the PNSTTQ in 13 on the other side of diaphragm t at a valueabove the operating pressure to relieve such high pressure ofoverheating below rupture or bursting pressure. Thus, when the pressureof the liquid in ti internal volume becomes greater than the gaspressure in 1 .3, 'hragm :3 will move into space to relieve the excesspessur-e on the liquid, without impairing or ctr. the operation of theliquid for its intended use at pressures below this relief pressure.

A mo fication of my invention is shown in 3. shown a Bourdon tubeconnected to a tube i-ll, on tube 41 is connected to bulb 413. D'tendingfrom tube M is stainless steel tube :3. Tube extends within pressurechamber i4 and within the pressure chamber i is flattened as shown atand sealed at its tip 46. P cs e chamber surrounding the flatte edportion 45 this portion of the tube in flattened condition until thepressure within tube and flattened portion 55 begins to equal thepressure in pressure chamber 44 at which time the fla ened portion tendsto become circular in cross section and in expanding enlarges the volumeto provide a safety pressure release for the liquid in the internalvolume of Bourdon tube 40, tube 41, bulb 42, tube 5.3 and its flattenedportion 45.

Tube 43 is so flattened as shown at 45 that substantially no liquid ispresent Within the flattened portion 45 of tube 43 so that the pressurewithin the pressure chamber 44 is not transmitted to the liquid withinthe internal volume of tube 43, tube 41, Bourdon tube 4d and bulb 47..With this arrangement the pressure on the internal volume is independentof the pressure in the pressure chamber 44 until the pressure of theliquid in the internal volume approaches the pressure in the pressurechamber 44 and the flattened portion 43 begins to expand against thepressure in the pressure chamber.

Fig. 4 shows a plot of the relationship between the pressure developedon the internal volume of this system of this particular embodiment ofmy invention, with acetone as the liquid, and with the bulb a stainlesssteel tube having an internal diameter of about 1 centimeter and havingan internal volume of 17 cubic centimeters connected to a Bourdon tubeby way of tube 41 with the Bourdon tube and tube 41 having a volume ofonly about 0.1 cubic centimeters. The temperature plotted is thetemperature of the bulb and its internal liquid. The pressure plotted isthe pressure of this internal liquid as measured by movement of theBourdon tube. Thi system was filled with acetone and adjusted to operateat a temperature of 70 F. at an internal pressure of 400 pounds persquare inch with the bulb at 70 F. in Fig. 4, curve 30 shows therelationship between the temperature of the bulb and the resultingpressure. The curve represents results of measurements. With a nitrogenpressure of 930 pounds per square inch in pressure chamber 44 theflattened portion 45 begins to relieve the pressure on the liquid asshown at 31 on the curve in Fig. 4 so that the pressure in the internalvolume does not rise above 930 pounds per square inch as relieved by theflattened portion 45. Curve 33 shows the relationship between the vaporpressure of acetone and its temperature. At point 32 corresponding witha temperature of about 63.5 F. the liquid in this system is just at thepoint of transition from the condition of liquid lock to the conditionwhere below said temperature of 635 F. the pressure varies in accordancewith the vapor pressure of the liquid in accordance with its averagetemperature. The device of my invention uses particularly thatportion ofthe curve from'point 32 to portion 31. It will be noted that thisportion of the curve is very steep and represents a rate change ofpressure with temperature of about 55 pounds per square inch per degreeFahrenheit. Thus it will be seen that within the range of temperaturesof about 63 to 80"v R, which embraces the control point of 70 R, mydevice is exceedingly and eminently sensitive to small changes intemperature.

It. is an important consideration in accordance with my invention that,in addition to the presence, at the operating temperature,.of liquidunder the liquid lock condition in the internal volume of temperaturesensing bulb and pressure responsive means such as Bourdon tube, theresulting change in internal volume of this liquid with change intemperature is translated as much as possible and to a surprising extentinto movement of the Bourdon tube so that maximum movement of theBourdon tube is obtained per unit change in temperature. Since theBourdon tube movement depends on the change in pressure, the change inpressure is representative of the movement of the Bourdon tube in anyparticular system in accordance with my invention, as indicated, forexample, in Fig. 4. Itshould be noted especially that in accordance.with my invention the volume change with change in temperature issubstantially all translated into movement of the Bourdon tube. Thus, myinvention clearly distinguishes from a systemin which a bellows is used,in-

stead of a Bourdon tube in the combination, because the change in volumeof a bellows with the change in volume of the liquid with thermalexpansion does not produce sufficient movement of the temperatureresponsive device as is produced in accordance with my invention. Thisarises in accordance with my invention chiefly because there issubstantially no, or only very limited, change of internal volume of mysystem with changes in temperature of the liquid. It will be understood,of course, that such factors as compressibility of the liquid withincrease in pressure and some slight expansion of the temperaturesensing bulb and Bourdon tube are operating in all systems to slightlyreduce the movement of the temperature responsive device, but inaccordance with my invention the movement of the temperature responsivedevice, especially for use in operating a thermostat, is exceedingly andsurprisingly high per unit change of temperature of the temperaturesensing bulb. In this connection it is preferred in accordance with myinvention to select a liquid which, for the conditions of operation, hasa satisfactorily high pressure change with temperature in this system.However, in accordance with my invention it is possible to take thegreatest advantage of such pressure change of any liquid to produce asurprisingly high effective and useful movement of the temperatureresponsive device, especially for use in a thermostat, particularly foroperating electrical contact points or snap acting electrical switches,especially those known in the art as microswitches.

It is preferred that in the device in accordance with my invention thatthe internal volume of the temperature sensing bulb be sufficientlylarge with respect to the rest of the internal volume so that the deviceis substantially entirely sensitive to changes in temperature of thebulband relatively unaffected by changes in temperature of the Bourdon tube.Usually the volume of the bulb will be at least 90 per cent of of theinternal volume of the system.

This application is a continuation-impart of my co- 6 pendingapplication Serial No. 300,720, filed July 24, 1952.

The specific embodiments given above are for the purpose of illustratingmy invention, and it will be readily understood that my inventionincludes other modifications within the scope of the following claims.

I claim:

1. In a temperature responsive device, the combination comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition and ata pressure above the vapor pressure of said liquid at the operatingtemperature so that changes of pressure of said liquid vary with thethermal expansion of said liquid in accordance with the averagetemperature thereof.

2. In a temperature responsive device, the combination comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition at theoperating temperature so that changes of pressure of said liquid varywith the thermal expansion of said liquid in accordance with the averagetemperature thereof, and means for relieving excessive pressuredeveloped on said liquid within said internal volume to avoid damage tosaid device arising from such excessive pressure.

3. In a temperature responsive device, the combination comprising atemperature sensing element filled with liquid and means connectedthereto responsive to changes of pressure of said liquid with changes oftemperature thereof, said means being so responsive to said changes ofpressure with substantially no change of internal volume thereof, saidliquid within the internal volume of said sensing element and meansbeing in the liquid lock condition at the operating temperature so thatchanges of pressure of said liquid vary with the thermal expansion ofsaid liquid in accordance with the average temperature thereof, andmeans for relieving excessive pressure developed on said liquid withinsaid internal volume to avoid damage to said device arising from suchexcessive pressure.

4. In a temperature responsive device, the combination comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition at theoperating temperature so that changes of pressure of said liquid varywith the thermal expansion of said liquid in accordance with the averagetemperature thereof, and means for relieving excessive pressuredeveloped on said liquid within said internal volume to avoid damage tosaid device arising from such excessive pressure comprising a diaphragm,one side of which is on contact with the pressure of said liquid and theother side of which is subjected to gas under the pressure at which saidmeans relieves said excessive pressure.

5. In a temperature responsive device, the combination comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition at theoperating temperature so that changes of pressure of said liquid varywith the thermal expansion of said liquid in accordance with the averagetemperature thereof, and means for relieving excessive pressuredeveloped on said liquid within said internal volume to avoid damage tosaid device arising from such excessive pressure, said means comprisinga diaphragm subject to said liquid pressure on one side and on the otherside subject to the relief pressure, said diaphragm being movable torelease the pressure on said liquid when it becomes greater than thepressure on the other side of said diaphragm.

6. In a temperature responsive device, the combination comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition at theoperating temperature so that changes of pressure of said liquid varywith the thermal expansion of said liquid in accordance with the averagetemperature thereof, and means for relieving excessive pressuredeveloped on said liquid within said internal volume to avoid damage tosaid device arising from such excessive pressure, said means comprisinga flattened portion of a tube within a pressure chamber, said flattenedportion adapted to expand and relieve the pressure on said liquid whenit becomes greater than the pressure in said pressure chamber.

7. In a temperature responsive device, the combinaion comprising atemperature sensing element and a Bourdon tube the internal volume ofwhich is entirely filled with liquid in the liquid lock condition at theoperating temperature so that changes of pressure of said liquid varywith the thermal expansion of said liquid in accordance with the averagetemperature thereof, the internal volume of said temperature sensingelement being at least 90 percent of the internal volume of the systemconsisting of said Bourdon tube and said temperature sensing element.

8, In a temperature responsive device, the combination comprising atemperature sensing element filled with liquid and means connectedthereto responsive to changes of pressure of said liquid with changes oftemperature thereof with substantially no change of internal volumethereof, the internal volume of said element and said means beingentirely filled with liquid in the liquid lock condition and at apressure above the vapor pressure of said liquid at the operatingtemperature of said temperature responsive device so that changes ofpressure of said liquid vary with the thermal expansion of said liquidin accordance with the average temperature thereof.

9. A temperature responsive device as defined in claim 8 having meansfor relieving excessive pressure developed on said liquid within saidinternal volume to avoid damage to said device arising from suchexcessive pressure.

10. A temperature responsive device as defined in claim 8 having meansfor relieving excessive pressure developed on said liquid within saidinternal volume to avoid damage to said device arising from suchexcessive pressure comprising a diaphragm, one side of which is oncontact with the pressure of said liquid and the other side of which issubjected to gas under the pressure at which said means relieves saidexcessive pressure.

ll. A temperature responsive device as defined in claim 8 having meansfor relieving excessive pressure developed on said liquid within saidinternal volume to avoid damage to said device arising from suchexcessive pressure, said means comprising a diaphragm subject to saidliquid pressure on one side and on the other side subject to the reliefpressure, said diaphragm being movable to release the pressure on saidliquid when it becomes greater than the pressure on the other side ofsaid diaphragm.

12. A temperature responsive device as defined in claim 8 having meansfor relieving excessive pressure developed on said liquid within saidinternal volume to avoid damage to said device arising from suchexcessive pressure, said means comprising a flattened portion of a tubewithin a pressure chamber, said flattened portion adapted to expand andrelieve the pressure on said liquid when it becomes greater than thepressure in said pressure chamber.

13. A temperature responsive device as defined in claim 8 in which theinternal volume of said temperature sensing element is at least 90percent of the internal volume of the system consisting of said meansand said temperature sensing element.

14. A temperature responsive device as defined in claim 3 in which saidmeans for relieving excessive pressure relieves said excessive pressurewithout any substantial drop in pressure of said liquid at the pressurevalue at which said relief is effected.

References Cited in the file of this patent UNITED STATES PATENTS

